I/Q Compensation of Broadband Direct-Conversion Transmitters

Abstract

The aim of this paper is to propose a compensation strategy that is able to easily identify the model of the Inphase/Quadrature (I/Q) impairments of Radio-Frequency (RF) direct-conversion devices and to efficiently compensate these unwanted effects. In fact, direct-conversion transmitters that integrate analog and digital components introduce a wideband frequency-dependent I/Q mismatch that strongly reduces the upconverter performances. The wider the signal bandwidth or the higher its spectral efficiency, the more severe the I/Q artifacts on the upconverted signal become. The proposed compensation strategy can mitigate these unwanted effects, eliminating I/Q impairments with a very simple hardware architecture. The compensation model adopted here for a generic upconverter device does not assume any hypotheses about signal modulation and system architecture and can be easily adapted to accommodate specific hardware systems or different wireless standards. To show the capabilities of the proposed compensation scheme, an experimental setup has been arranged to emulate system configurations found in direct-conversion RF Integrated Circuits (RFIC) for 3.5/4G applications.

Joint Effects of Residual Hardware Impairments and Channel Estimation Errors on SWIPT Assisted Cooperative NOMA Networks

“…In practice, by deploying low-cost and low power components, all RF front-ends are prone hardware imperfections, and they suffer from a variety of hardware impairments, such as phase noise, in phase/quadrature phase (I/Q) imbalance, high power amplifier nonlinearity and quantization error [21], [22]. To this end, a great deal of works have proposed many algorithms to compensate the loss caused by hardware impairments [23]- [25]. However, the residual hardware impairments have significant effects on the system performance, authors in [26] studied the system effects of multiplerelay AF network in the presence of RHIs and derived the closed-form expression of the outage probability.…”

Compensation of Delay Mismatch in a Direct Conversion Transmitter

“…A significant portion of research is dedicated to the I/Q impairment compensation [4]- [8] with an assumption that the DM is negligible and ignored. The assumption is valid for narrowband communications systems; however, it is no longer the case in wideband systems.…”

“…These techniques require a complex feedback circuit and/or complex algorithm to synchronize the transmitted I/Q signals and feedback I/Q signals. An incoherent measurement is presented to estimate and compensate for the frequency-selective I/Q imbalances in DCT, which avoids the synchronization [8]. This brief theoretically analyzes the performance degradation in terms of image rejection ratio (IRR) due to the DM.…”

I/Q Imbalance Estimation for Direct Conversion Receivers by Jointly Using the Existing Preambles and Blind Estimation

“…These methods required exclusive pilot signals for I/Q imbalances estimation, and consequently resulted in an additional overhead. Another popular approach for I/Q imbalances estimation was via onchip loopback [5], [6]. However, the on-chip loopback was able to operate only in the start-up stage of the chip.…”